Integrated circuits are manufactured from workpieces that are typically created by growing an elongated cylinder or boule of single crystal silicon and slicing the individual workpieces from the cylinder. Slicing may cause one or both faces of the workpiece to be somewhat rough. However, at least the front face of the workpiece on which integrated circuitry is to be constructed should be substantially flat in order to facilitate reliable semiconductor junctions formed from subsequent layers of material that are applied to the workpiece. Thus, chemical-mechanical polishing (CMP) is performed on each workpiece to remove projections and other imperfections to create a smooth planar surface. Once the workpiece surface is planarized, composite thin film layers comprising metals for conductors or oxides for insulators then may be deposited over the workpiece. These layers preferably have a uniform thickness for joining to the semiconductor workpieces or to other composite thin film layers. CMP may be employed to planarize the thin film layers.
Typically, a CMP assembly includes a workpiece carrier connected to a shaft. The shaft may be connected to a transporter that moves the carrier between a load or unload station and a position adjacent to a polishing pad. One side of the polishing pad has a polishing surface thereon, and an opposite side is mounted to a rigid platen. Pressure is exerted on a workpiece back surface by the carrier in order to press a workpiece front surface against the polishing pad. Polishing fluid is introduced onto the polishing surface while the workpiece and/or polishing pad are moved in relation to each other by means of motors connected to the shaft and/or platen in order to remove material from the workpiece front surface. After each polishing operation, contaminants, such as removed workpiece material, may be deposited on the polishing pad. Thus, the polishing pad is swept with a conditioning bar to remove the contaminants.
Ideally, tool parameters of the CMP assembly, such as down force pressure exerted by the polishing pad against the workpiece, and/or down force pressure exerted by the conditioning bar against the polishing pad, are set at values that will yield high quality workpieces. However, because some of the tool components, in particular, consumable components such as polishing pads and conditioning bars, become worn with increased use, the tool parameter values may need to be adjusted from time to time. Typically, these adjustments are based upon the number of workpiece operations that have been performed using a particular consumable component.
Although the above-mentioned tool parameter adjustment method is generally effective, it may suffer from drawbacks in certain applications. For example, because the tool parameter adjustments are based, in large part, upon the number of workpieces that are run through the tool, actual tool and workpiece conditions may not be taken into account. This may present issues for a CMP assembly that employs an eddy current probe for determining a metal layer thickness on a workpiece. In particular, the eddy current probe typically generates a magnetic field and then detects a magnetic flux change in the magnetic field when the workpiece metal layer is passed therethrough. The magnetic flux change is influenced, in part, by the distance between the probe and the metal layer. Thus, in cases in which workpieces are disposed on a polishing pad while the eddy current probe obtains its measurement, the diminishing thickness of the polishing pad may cause each workpiece to become increasingly closer to the probe. As a result, the measured metal layer thickness of the workpiece may not be as accurate as desired. Another consequence of using number of operations for adjusting tool parameters may be that some of the consumable components may not be used to their optimal useful life.
Accordingly, it is desirable to have a tool that not only yields high quality workpieces, but also accurately optimizes tool parameters. In addition, it is desirable to have a tool that is capable of optimizing the useful life of its consumable components. Moreover, it is desirable for the tool to indicate an accurate measurement of an amount of metal deposited on a workpiece. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.